Staphylococcus aureus (staph) bacteria are a common component of the skin surface and lining of the nasal passageways in humans and other animals, and are usually spread by skin-to-skin contact. Methicillin-resistant S. aureus (MRSA) is a strain of S. aureus that has become resistant to methicillin, an antibiotic commonly used to treat ordinary S. aureus infections. As such, MRSA is particularly hard to treat. When limited to the skin surface and lining of the nasal passageways, S. aureus bacteria are normally harmless. However, S. aureus infections can occur in situations where the bacteria enter into the skin subsurface or body cavity, normally through wounds (including, e.g., surgical incisions) or other sites such as hair follicles.
MRSA infections often occur in patients having weakened immune systems who have been exposed to MRSA, such as patients in long term care, patients undergoing kidney dialysis, or patients recovering from recent surgery or medical treatments such as chemotherapy that weaken the immune system. Skin wounding events or other forms of compromise to skin integrity (e.g., intravenous drug use) are another major risk for MRSA infection, which risk may or may not coincide with the exposure risk. MRSA is often acquired or develops in medical care facilities, such as hospitals. This type of MRSA is known as health care-associated MRSA (HA-MRSA). But MRSA can also develop in otherwise healthy people not exposed to hospital situations. In these situations, it is termed community-acquired MRSA (CA-MRSA). CA-MRSA has often been found to be acquired by athletes (who may share towels and razors), children in day care, members of the military and people obtaining tattoos, for example.
Symptoms of staph infections may include red, swollen and painful boil-like symptoms, which may be treated locally. In severe cases and in hospital situations, staph infections may be systemic and must be treated with systemically administered antibiotics.
Some individuals seem to be uniquely susceptible to staph infections and developing recurrent CA-MRSA skin infections. Such populations may also have an elevated risk for developing MRSA if admitted to medical care facilities. Treatment for these individuals involves attempts to decolonize the skin and nasal passages of the patient with topical antibiotics, which can be temporarily effective, especially when coupled with improved sanitation such as frequent hand washing and isolation from other patients. Thus, improved methods of recognizing persons susceptible to recurrent MRSA and/or CA-MRSA are needed and can improve patient care and reduce the incidence of MRSA in these individuals.